How to do decompostion equations

Ok...I'm not entirely sure how to do decompostion equations (balancing) since i just learned it today but...

Al2O3------> ?

I think that the oxygen becomes an O2because it is a diatomic molecule. That I understand.

Do I have to carry the Al2 over so that the factors end up being 3Al2 + O2.....the thing is...that wouldn't work with the beginning of the equation because the first Al would be 4 while the factors Al would be 6..when I say this i mean the final equation would be like......2Al2O3----> 3Al2 + O2

I hope that makes sense!! I need this for homework and that is how I figured the problem above...if someone could help me...that'd be amazing!!

Not quite. I'll give you an example...write the formula for potassium sulfide. KxSy

Think about the charges of K and S. K has a 1+ charge and S has a 2- charge. You should've been taught that you can figure that out by looking at the periodic table and counting to see how many electrons it needs to gain or lose to have an electron configuration of a noble gas.

The positive charges and negative charges have to be equal so that the compound is neutral. Thus, x = 2 and y = 1, so the answer would be K2S. Do you see why?

Here's another example, but this one invovles oxygen. Write out the formula for calcium oxide. Ca has a 2+ charge and oxygen has a 2- charge, therefore, it will simply be CaO.